In modern measuring devices, especially in modern digital oscilloscopes, a huge number of periodic measuring portions of a signal to be measured and to be displayed per time unit are acquisitioned. In future digital oscilloscopes about 1,000,000 acquisitions per second are determined. Thus updating the display in a period of 30 milliseconds leads to about 33,000 acquisitions per update cycle to be handled in a display memory of the oscilloscope.
A modern measuring device has to offer the two following display features to a user:                A histogram showing the statistical distribution of the sampled values of the measuring signal over all the acquisitions within an update cycle: The brightness or the color of each pixel enables the user to recognize, how many sampled values of the measured signal over all the acquisitions within an update cycle falls within the sampled value range and the time point resp. the frequency bin of the corresponding pixel as shown in FIG. 1. This feature for example enables the display of the noise behavior of the measured signal;        a display of a rare or singular occurrence of a sampled value within the sampled value range and the time point resp. the frequency bin of the corresponding pixel: This feature, for example, enables the display of a sporadic anomaly—i.e. a spike—in the measured signal.        
If 135,000 acquisitions are measured in an update cycle, one single pixel per column of the display can be hit 135,000 times in an update cycle in the worst case. Taking into account this worst case, each memory cell in the display memory assigned to a specific pixel of the display has to store a data of ld(33,000)=16 bits. Thus, in case of a display memory with 1250×800 memory cells, a memory capacity of 16 MBits for each display memory is necessary, i.e. applying 4 display memories the total size is 64 MBit. Using an ASIC for implementing such a display memory disadvantageously results in a comparatively too large portion of the total chip area for memory purpose (for example more than 50% of the total chip area).
In US 2009/0309879 A1 the number of bits in each memory cell of a display memory is reduced by decreasing the probability of incrementation of the frequency value stored in a memory cell in case of a hit of the corresponding pixel by a measured sampled value in dependency of the size of the frequency value actually stored in the memory cell.
The histogram of the measuring signal determined in US 2009/0309879 A1 does disadvantageously not represent the original statistical distribution of the measuring signal, because lower frequency values are taken into account in the histogram with a comparatively higher weighting than higher frequency values.
Therefore, one object is develop a measuring device, a corresponding method and a respective computer program with a reduced number of bits in each memory cell of the display memory enabling a more realistic representation of the statistical distribution of the measured signal in the display.